Tanaka ACL-2 Automatic Petroleum Colorimeter

Overview

The Tanaka ACL-2 Automatic Petroleum Colorimeter is a precision optical instrument engineered for standardized color assessment of liquid petroleum products, including lubricating oils, diesel fuels, naphthas, and refined solvents. It operates on the principle of tristimulus colorimetry as defined in JIS K 2580, replicating the visual perception of human observers under controlled illumination and geometry. The system employs a calibrated halogen light source (12 V / 20 W), a set of interference-grade colored glass filters, and high-speed silicon photodiodes to quantitatively measure spectral transmittance across the visible spectrum. By digitally emulating the Saybolt and ASTM D1500/D156 visual comparison methods—without reliance on subjective operator judgment—the ACL-2 delivers objective, repeatable, and traceable color values compliant with international standard test procedures. Its dual-mode architecture enables seamless switching between Saybolt color (0–80 scale) and ASTM color (0.5–8.0 scale), while also supporting APHA (Platinum-Cobalt) and Gardner color scales per ISO 2211, ISO 6271, and ISO 4630, respectively.

Key Features

• Tristimulus optical design conforming to JIS K 2580, ensuring metrological equivalence to ASTM D156 and D1500 reference methods
• High-speed 16-bit A/D conversion with low-drift photodetector electronics for measurement stability and repeatability
• Integrated fluorescent display (256 × 64 pixels) with real-time parameter visualization: Saybolt L*a*b*, ΔL*, Δa*, Δb*, ΔE*; ASTM X, Y, Z, ΔX, ΔY, ΔZ, ΣΔ
• Automated calibration routines: single-point or multi-point standardization using certified reference fluids
• Dual sample chamber configuration: 33 mm diameter cuvette for ASTM color testing; 100 mm diameter cell for Saybolt measurements
• Thermal printer (80 mm width) with embedded RS-232C interface for audit-ready hardcopy output and external data logging
• Modular flow-cell compatibility (optional) for integration into automated QC lines or continuous monitoring loops

Sample Compatibility & Compliance

The ACL-2 accommodates clear, transparent, and low-turbidity petroleum liquids within specified viscosity and volatility ranges. It is validated for use with mineral oils, white oils, kerosene, jet fuel, and hydrocarbon solvents meeting ASTM D4057 sampling protocols. Instrument performance and reporting comply with ASTM D6045 (standard practice for instrumental color measurement of petroleum products), JIS K 2550 (petroleum product color test method), and relevant clauses of ISO/IEC 17025 for testing laboratories. Data integrity is maintained through non-volatile memory storage and time-stamped measurement records. While not inherently 21 CFR Part 11 compliant, its RS-232C interface supports integration with validated LIMS platforms that enforce electronic signature, audit trail, and user access control requirements under GLP/GMP frameworks.

Software & Data Management

The ACL-2 operates via embedded firmware with menu-driven navigation optimized for routine laboratory workflows. All color calculations—including CIELAB transformations and delta-E evaluation—are performed internally using factory-loaded algorithms traceable to NIST-traceable standards. Measurement data are output in ASCII format via RS-232C, enabling direct ingestion into spreadsheet applications or enterprise quality systems. Optional PC-based software (sold separately) provides extended functionality: batch report generation, trend analysis over time, statistical process control (SPC) charting, and export to CSV or PDF formats. Calibration history, operator ID (via manual entry), and environmental metadata (e.g., ambient temperature at time of test) are recorded with each measurement to support ISO 17025 documentation requirements.

Applications

• Quality control of base oils and finished lubricants during refining and blending operations
• Monitoring color stability of aviation turbine fuels per ASTM D1655 Annex A1
• Batch release testing of pharmaceutical-grade white mineral oil (USP/EP specifications)
• Regulatory compliance verification for diesel fuel color per EN 590 and ASTM D975
• Research and development of oxidation-inhibited formulations where color shift indicates degradation onset
• Interlaboratory method transfer studies requiring harmonized color data across global sites

FAQ

Does the ACL-2 require annual recalibration by an accredited service provider?

No mandatory annual recalibration is specified; however, users must perform periodic verification using certified reference standards (e.g., Saybolt color standards SRM 1936 series or APHA platinum-cobalt solutions) prior to critical testing, in accordance with ASTM D6045 Section 8.
Can the ACL-2 measure opaque or highly viscous samples?

No—it is designed exclusively for transparent, low-absorbance liquids. Samples exceeding 50 cSt at 40 °C or exhibiting haze >5 NTU require pre-filtration or dilution per ASTM D4176 and D5257 guidelines.
Is the instrument compatible with modern LIMS or ELN platforms?

Yes, via its RS-232C serial interface and ASCII output protocol; integration requires middleware configuration or custom driver development aligned with site-specific IT validation protocols.
What is the typical measurement repeatability for Saybolt color readings?

Under controlled conditions (23 ± 2 °C, stable power supply), repeatability is ≤ ±0.5 Saybolt units for homogeneous samples tested in triplicate using the same cuvette and operator.
Are replacement halogen lamps and color standard kits available from Tanaka directly?

Yes—original equipment manufacturer (OEM) lamps (12 V / 20 W) and NIST-traceable color reference sets (Saybolt, ASTM, APHA, Gardner) are supplied through Tanaka’s authorized distribution network with documented lot traceability.